// imported from https://github.com/socketio/engine.io-parser/tree/2.2.x

/**
 * Module dependencies.
 */

var utf8 = require('./utf8');

/**
 * Current protocol version.
 */
exports.protocol = 3;

const hasBinary = (packets) => {
  for (const packet of packets) {
    if (packet.data instanceof ArrayBuffer || ArrayBuffer.isView(packet.data)) {
      return true;
    }
  }
  return false;
}

/**
 * Packet types.
 */

var packets = exports.packets = {
    open:     0    // non-ws
  , close:    1    // non-ws
  , ping:     2
  , pong:     3
  , message:  4
  , upgrade:  5
  , noop:     6
};

var packetslist = Object.keys(packets);

/**
 * Premade error packet.
 */

var err = { type: 'error', data: 'parser error' };

const EMPTY_BUFFER = Buffer.concat([]);

/**
 * Encodes a packet.
 *
 *     <packet type id> [ <data> ]
 *
 * Example:
 *
 *     5hello world
 *     3
 *     4
 *
 * Binary is encoded in an identical principle
 *
 * @api private
 */

exports.encodePacket = function (packet, supportsBinary, utf8encode, callback) {
  if (typeof supportsBinary === 'function') {
    callback = supportsBinary;
    supportsBinary = null;
  }

  if (typeof utf8encode === 'function') {
    callback = utf8encode;
    utf8encode = null;
  }

  if (Buffer.isBuffer(packet.data)) {
    return encodeBuffer(packet, supportsBinary, callback);
  } else if (packet.data && (packet.data.buffer || packet.data) instanceof ArrayBuffer) {
    return encodeBuffer({ type: packet.type, data: arrayBufferToBuffer(packet.data) }, supportsBinary, callback);
  }

  // Sending data as a utf-8 string
  var encoded = packets[packet.type];

  // data fragment is optional
  if (undefined !== packet.data) {
    encoded += utf8encode ? utf8.encode(String(packet.data), { strict: false }) : String(packet.data);
  }

  return callback('' + encoded);
};

/**
 * Encode Buffer data
 */

function encodeBuffer(packet, supportsBinary, callback) {
  if (!supportsBinary) {
    return exports.encodeBase64Packet(packet, callback);
  }

  var data = packet.data;
  var typeBuffer = Buffer.allocUnsafe(1);
  typeBuffer[0] = packets[packet.type];
  return callback(Buffer.concat([typeBuffer, data]));
}

/**
 * Encodes a packet with binary data in a base64 string
 *
 * @param {Object} packet, has `type` and `data`
 * @return {String} base64 encoded message
 */

exports.encodeBase64Packet = function(packet, callback){
  var data = Buffer.isBuffer(packet.data) ? packet.data : arrayBufferToBuffer(packet.data);
  var message = 'b' + packets[packet.type];
  message += data.toString('base64');
  return callback(message);
};

/**
 * Decodes a packet. Data also available as an ArrayBuffer if requested.
 *
 * @return {Object} with `type` and `data` (if any)
 * @api private
 */

exports.decodePacket = function (data, binaryType, utf8decode) {
  if (data === undefined) {
    return err;
  }

  var type;

  // String data
  if (typeof data === 'string') {

    type = data.charAt(0);

    if (type === 'b') {
      return exports.decodeBase64Packet(data.substr(1), binaryType);
    }

    if (utf8decode) {
      data = tryDecode(data);
      if (data === false) {
        return err;
      }
    }

    if (Number(type) != type || !packetslist[type]) {
      return err;
    }

    if (data.length > 1) {
      return { type: packetslist[type], data: data.substring(1) };
    } else {
      return { type: packetslist[type] };
    }
  }

  // Binary data
  if (binaryType === 'arraybuffer') {
    // wrap Buffer/ArrayBuffer data into an Uint8Array
    var intArray = new Uint8Array(data);
    type = intArray[0];
    return { type: packetslist[type], data: intArray.buffer.slice(1) };
  }

  if (data instanceof ArrayBuffer) {
    data = arrayBufferToBuffer(data);
  }
  type = data[0];
  return { type: packetslist[type], data: data.slice(1) };
};

function tryDecode(data) {
  try {
    data = utf8.decode(data, { strict: false });
  } catch (e) {
    return false;
  }
  return data;
}

/**
 * Decodes a packet encoded in a base64 string.
 *
 * @param {String} base64 encoded message
 * @return {Object} with `type` and `data` (if any)
 */

exports.decodeBase64Packet = function(msg, binaryType) {
  var type = packetslist[msg.charAt(0)];
  var data = Buffer.from(msg.substr(1), 'base64');
  if (binaryType === 'arraybuffer') {
    var abv = new Uint8Array(data.length);
    for (var i = 0; i < abv.length; i++){
      abv[i] = data[i];
    }
    data = abv.buffer;
  }
  return { type: type, data: data };
};

/**
 * Encodes multiple messages (payload).
 *
 *     <length>:data
 *
 * Example:
 *
 *     11:hello world2:hi
 *
 * If any contents are binary, they will be encoded as base64 strings. Base64
 * encoded strings are marked with a b before the length specifier
 *
 * @param {Array} packets
 * @api private
 */

exports.encodePayload = function (packets, supportsBinary, callback) {
  if (typeof supportsBinary === 'function') {
    callback = supportsBinary;
    supportsBinary = null;
  }

  if (supportsBinary && hasBinary(packets)) {
    return exports.encodePayloadAsBinary(packets, callback);
  }

  if (!packets.length) {
    return callback('0:');
  }

  function encodeOne(packet, doneCallback) {
    exports.encodePacket(packet, supportsBinary, false, function(message) {
      doneCallback(null, setLengthHeader(message));
    });
  }

  map(packets, encodeOne, function(err, results) {
    return callback(results.join(''));
  });
};

function setLengthHeader(message) {
  return message.length + ':' + message;
}

/**
 * Async array map using after
 */

function map(ary, each, done) {
  const results = new Array(ary.length);
  let count = 0;

  for (let i = 0; i < ary.length; i++) {
    each(ary[i], (error, msg) => {
      results[i] = msg;
      if (++count === ary.length) {
        done(null, results);
      }
    });
  }
}

/*
 * Decodes data when a payload is maybe expected. Possible binary contents are
 * decoded from their base64 representation
 *
 * @param {String} data, callback method
 * @api public
 */

exports.decodePayload = function (data, binaryType, callback) {
  if (typeof data !== 'string') {
    return exports.decodePayloadAsBinary(data, binaryType, callback);
  }

  if (typeof binaryType === 'function') {
    callback = binaryType;
    binaryType = null;
  }

  if (data === '') {
    // parser error - ignoring payload
    return callback(err, 0, 1);
  }

  var length = '', n, msg, packet;

  for (var i = 0, l = data.length; i < l; i++) {
    var chr = data.charAt(i);

    if (chr !== ':') {
      length += chr;
      continue;
    }

    if (length === '' || (length != (n = Number(length)))) {
      // parser error - ignoring payload
      return callback(err, 0, 1);
    }

    msg = data.substr(i + 1, n);

    if (length != msg.length) {
      // parser error - ignoring payload
      return callback(err, 0, 1);
    }

    if (msg.length) {
      packet = exports.decodePacket(msg, binaryType, false);

      if (err.type === packet.type && err.data === packet.data) {
        // parser error in individual packet - ignoring payload
        return callback(err, 0, 1);
      }

      var more = callback(packet, i + n, l);
      if (false === more) return;
    }

    // advance cursor
    i += n;
    length = '';
  }

  if (length !== '') {
    // parser error - ignoring payload
    return callback(err, 0, 1);
  }

};

/**
 *
 * Converts a buffer to a utf8.js encoded string
 *
 * @api private
 */

function bufferToString(buffer) {
  var str = '';
  for (var i = 0, l = buffer.length; i < l; i++) {
    str += String.fromCharCode(buffer[i]);
  }
  return str;
}

/**
 *
 * Converts a utf8.js encoded string to a buffer
 *
 * @api private
 */

function stringToBuffer(string) {
  var buf = Buffer.allocUnsafe(string.length);
  for (var i = 0, l = string.length; i < l; i++) {
    buf.writeUInt8(string.charCodeAt(i), i);
  }
  return buf;
}

/**
 *
 * Converts an ArrayBuffer to a Buffer
 *
 * @api private
 */

function arrayBufferToBuffer(data) {
  // data is either an ArrayBuffer or ArrayBufferView.
  var length = data.byteLength || data.length;
  var offset = data.byteOffset || 0;

  return Buffer.from(data.buffer || data, offset, length);
}

/**
 * Encodes multiple messages (payload) as binary.
 *
 * <1 = binary, 0 = string><number from 0-9><number from 0-9>[...]<number
 * 255><data>
 *
 * Example:
 * 1 3 255 1 2 3, if the binary contents are interpreted as 8 bit integers
 *
 * @param {Array} packets
 * @return {Buffer} encoded payload
 * @api private
 */

exports.encodePayloadAsBinary = function (packets, callback) {
  if (!packets.length) {
    return callback(EMPTY_BUFFER);
  }

  map(packets, encodeOneBinaryPacket, function(err, results) {
    return callback(Buffer.concat(results));
  });
};

function encodeOneBinaryPacket(p, doneCallback) {

  function onBinaryPacketEncode(packet) {

    var encodingLength = '' + packet.length;
    var sizeBuffer;

    if (typeof packet === 'string') {
      sizeBuffer = Buffer.allocUnsafe(encodingLength.length + 2);
      sizeBuffer[0] = 0; // is a string (not true binary = 0)
      for (var i = 0; i < encodingLength.length; i++) {
        sizeBuffer[i + 1] = parseInt(encodingLength[i], 10);
      }
      sizeBuffer[sizeBuffer.length - 1] = 255;
      return doneCallback(null, Buffer.concat([sizeBuffer, stringToBuffer(packet)]));
    }

    sizeBuffer = Buffer.allocUnsafe(encodingLength.length + 2);
    sizeBuffer[0] = 1; // is binary (true binary = 1)
    for (var i = 0; i < encodingLength.length; i++) {
      sizeBuffer[i + 1] = parseInt(encodingLength[i], 10);
    }
    sizeBuffer[sizeBuffer.length - 1] = 255;

    doneCallback(null, Buffer.concat([sizeBuffer, packet]));
  }

  exports.encodePacket(p, true, true, onBinaryPacketEncode);

}


/*
 * Decodes data when a payload is maybe expected. Strings are decoded by
 * interpreting each byte as a key code for entries marked to start with 0. See
 * description of encodePayloadAsBinary

 * @param {Buffer} data, callback method
 * @api public
 */

exports.decodePayloadAsBinary = function (data, binaryType, callback) {
  if (typeof binaryType === 'function') {
    callback = binaryType;
    binaryType = null;
  }

  var bufferTail = data;
  var buffers = [];
  var i;

  while (bufferTail.length > 0) {
    var strLen = '';
    var isString = bufferTail[0] === 0;
    for (i = 1; ; i++) {
      if (bufferTail[i] === 255)  break;
      // 310 = char length of Number.MAX_VALUE
      if (strLen.length > 310) {
        return callback(err, 0, 1);
      }
      strLen += '' + bufferTail[i];
    }
    bufferTail = bufferTail.slice(strLen.length + 1);

    var msgLength = parseInt(strLen, 10);

    var msg = bufferTail.slice(1, msgLength + 1);
    if (isString) msg = bufferToString(msg);
    buffers.push(msg);
    bufferTail = bufferTail.slice(msgLength + 1);
  }

  var total = buffers.length;
  for (i = 0; i < total; i++) {
    var buffer = buffers[i];
    callback(exports.decodePacket(buffer, binaryType, true), i, total);
  }
};
